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Old 28th September 2004, 11:52 PM   #1
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Angry paralell gainclone not working

With no signal it remains cool, Add a small signal and it quickly gets hot .
I do have a star ground in the amp and in the psu.
RCAs are isolated.
.25 ohm on each output
no zobel


I know that some people have problems with Oscillation in the absence of input but my problem is the opposite.

also, could someone tell me if my implementation of the .25 ohm resisters on the outputs its the correct way to paralell two amps.
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Old 29th September 2004, 07:17 AM   #2
Netlist is offline Netlist  Belgium
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Could you post or point us to the schematic you used?

/Hugo
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Old 29th September 2004, 07:18 AM   #3
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Which IC do you use, LM3875 or LM3886?

How about the ground connections?

Picture and/or schermatics?

EDIT: Hugo too fast
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Old 29th September 2004, 03:52 PM   #4
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If possible, post a pic of the board too.

Oh, I like your name.
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Old 29th September 2004, 09:11 PM   #5
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Default lay out

Its pretty simple,
I just put two .5 ohm resisters back to back and soldered them together. Placing two legs in the OUT hole of the board and connecting a wire to the other two leggs Resulting in a .25 ohm in series with each boards output. I then connected the two wires(post resister) to each other and on to the positive output post on the chassis.

The amp acts as though it's output is shorted, but I tested that.

I am trying to add a pic and I don't know if its working but you can see the resisters mounted in the board, but there is nothing attached to them in one pic. In another pic, the blue and white wires are my output leads.
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Old 29th September 2004, 09:17 PM   #6
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Default the other pic

This pic has the wires attached to the outputs, White is positive, Blue is negitive.

also, I have taken care of the input ground going back to the other board. It is now going directly to the star ground
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Old 29th September 2004, 09:28 PM   #7
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Default BTW I used a 3875 chip

pic of the PSU.

Two 300 VA transformers connected by Two XLR connectors to the Amp.
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Old 29th September 2004, 10:21 PM   #8
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What's the voltage of the trafos?
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Old 29th September 2004, 10:39 PM   #9
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Default 22 volts

after rectification its around 70 volts (V- to V+)
35 Volts no load Ground to V+ and Ground to V-
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Old 29th September 2004, 10:49 PM   #10
troystg is offline troystg  United States
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Hi-

So you are paralleling two sets of the BrianGT boards.

Have you tested the boards individually?


Thanks,

Troy
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